A cis-3,4-di(furan-2-yl)cyclobutane-1,2-dicarboxylic
acid (CBDA-2) is readily prepared stereospecifically
from trans-3-(2-furyl)acrylic acid, a furfural-derived
compound, through a solid-state [2 + 2] photocycloaddition in 95%
isolated yield. The cyclobutane ring in CBDA-2 shows
desired stabilities during thermal, sunlight, and chemical tests.
The single crystal structure of CBDA-2 revealed the geometry
of this molecule and orientation of the two dicarboxylic acid groups
displaying its potential to serve as a unique, semirigid diacid building
block in material science. A preliminary study showed that condensation
of this diacid with glycerol yielded a green polymer with good stability.
The diacid could also be used as a cross-linker for a biobased epoxy
to yield an exceptionally hard and solvent-resistant thermoset.
Highly functional bio-based methacrylate and acrylate resins were synthesized from epoxidized sucrose soyate (ESS) and incorporated into formulations for stereolithographic (SLA) printing. These formulations were compared to a commercial SLA resin and with formulations where the bioderived resins were replaced with commercial urethane acrylates. The tensile, flexural, rheological, and thermomechanical performances of the respective formulations and their prints were compared. All of the formulations were able to be printed satisfactorily with a Peopoly Moai SLA 3D printer. The acrylated ESS resin showed the highest viscosity while the methacrylated ESS resins had lower viscosities than the control urethane acrylates. The prints made from the formulations containing the methacrylated ESS resins had similar T g s to that of the urethane acrylate control formulations while the prints from the acrylated ESS resin had a lower T g . The tensile and flexural properties were consistent with the T g values in terms of modulus, but some of the prints showed surface cracking that compromised the strength properties. This study demonstrated the ability of a bio-derived material to be functionally modified and incorporated into an SLA formulation and printed in different orientations.
A study was carried out to compare the epoxidation of unsaturated vegetable oils using dioxirane intermediates generated in situ using Oxone to that by the peracid/hydrogen peroxide method. Epoxidized oils are typically synthesized using hydrogen peroxide, as well as acetic or formic acid. This synthesis requires heating and catalysts and generates acidic waste. Recently, advances have been made in the process of using Oxone (potassium peroxymonosulfate) and ketones to generate in situ dioxiranes to epoxidize alkenes. The dioxirane method allows for room temperature reactions and eliminates the use of peroxides and acids. Epoxidation of soybean oil, hempseed oil and sucrose soyate using in situ generated dioxiranes was carried out and parameters such as molar ratios and addition rates were studied. The data show that optimum reaction conditions are reached when molar ratios of Oxone and unsaturation are 1.6:1 and the Oxone addition rate is 1 mL min -1 . As a comparison, epoxidations using the acetic acid/hydrogen peroxide method were carried out and cured materials were prepared from the epoxidized compounds. Negligible differences were identified in the materials prepared from both synthetic pathways. An environmental sustainability assessment using green chemistry principles was also conducted for both methods to evaluate their safety and efficiency with respect to multiple criteria including minimizing waste generation and energy consumption. The analysis shows that, although the peracid method is atom economic and generates less waste, the dioxirane method offers better occupational safety and requires less energy, demonstrating the tradeoffs involved with either pathway if one is to be selected.
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